Video compression methods reduce the bandwidth or storage requirements of digital video signals in applications such as High Definition (HD) television, video conferencing, video-on-demand, and multimedia communications. It is desirable to increase the amount of compression in digital video over established video compression formats without imposing unnecessary processing burden in the digital video compression while simultaneously preserving picture fidelity. Superior video compression performance is desirable for any of several technical and/or cost reasons, such as the reduction of bandwidth consumption in a transmission channel and/or the reduction of storage consumption.
The advent of video with larger picture resolution and/or frame rates, such as HD video, in televisions and consumer electronic (CE) devices is fostering a trend for additional HD or higher picture resolution television services, consequently resulting in higher bandwidth consumption in transmission channels and/or higher storage consumption. Increasing demand and requests for HD video services, higher picture fidelity, and user-dedicated bandwidth services, such as video-on-demand, pose challenges in management of transmission bandwidth and storage capacity.
However, service providers have invested in equipment and network infrastructure designed to support established video compression formats that correspond to the semantics and syntax of adopted video coding specifications, such as any of the existing video coding specifications documented by international standards. Established video compression formats have been around for some years, such as MPEG-2 (Motion Pictures Expert Group) Video. Likewise, consumers and service providers have invested CE products designed to support adopted video compression formats for interoperability reasons.
Although it is desirable to provide video compression performance better than what an adopted or “first” video compression format is capable of providing, it is also desirable to preserve investments in existing equipment, network infrastructure, and CE devices, by providing the capability to convert video from the established video compression format to a second video compression format that yields superior video compression performance. It is further desirable to leverage from information associated with the video coded with the first video compression format to reduce the processing burden in a compression engine that performs compression of the video into a second video compression format. Thus, it is desirable to accomplish the conversion of video from the first to the second video compression format while simultaneously maintaining minimum processing complexity and preserving the picture fidelity of the video signal.
A description of the aforementioned video coding international standards can be found in the following publications, which are hereby incorporated herein by reference: (1) ISO/IEC 11172-2 (1993): “Information technology—Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbits/s—Part 2: video;” (2) ITU-T Recommendation H-262 (1995)|ISO/IEC 13818-2 (1996): “Generic coding of moving pictures and associated audio information: Video;” (3) ITU-T Recommendation H.261 (1993): “Video codec for audiovisual services at p×64 kbits/s;” (4) ITU-T Recommendation H.263 (1998): “Video coding for low bit rate communication;” and (5) “ISO/IEC 14496-2 (2001): Information technology—Coding of audio-visual objects—Part 2: Visual.”
Many motion estimation methods are known. See for example U.S. Pat. No. 6,016,163 titled “Methods and apparatus for comparing blocks of pixels” and U.S. Pat. No. 6,195,389 titled “Motion estimation system and methods.” Typically, motion estimation is a computationally intense process, likely imposing the most processing and/or computational burden. Some motion estimation techniques consider not only offsets of an integer number of pixels, but also fractional pixel offsets, so that the search for a match is a particular computationally intense task.
It is an object of the system and methods disclosed herein to overcome the foregoing problems in motion estimation when converting video from a first to a second video compression format while simultaneously maintaining low processing complexity and preserving the picture fidelity of the video.